The bark beetle Dendroctonus mesoamericanus sp. nov. is described from a population in Parque Nacional Lagunas de Montebello, La Trinitaria, Chiapas, Mexico. This species belongs to the D. frontalis complex, which includes D. adjunctus Blandford 1897, D. approximatus Dietz 1890, D. brevicomis LeConte 1876, D. frontalis Zimmermann 1868, D. mexicanus Hopkins 1905, and D. vitei Wood 1975. The new species can be distinguished from closely related species D. frontalis, D. mexicanus, and D. vitei by four diagnostic morphological characters: the presence of striations on the preepisternal area of the prothorax (anterolateral pronotum) in both sexes, seminal rod with an approximately linear posterior margin of the dorsal process (in lateral view), irregularly sized ornamentations on the distal edge of squamiform plates present on the eighth abdominal tergite in females, and an inconspicuous pronotal callus in females. Furthermore, the karyotype of D. mesoamericanus sp. nov. (5AA Xyp / XX) differs from that of its sister species D. frontalis (7AA Xyp/XX). Dendroctonus mesoamericanus sp. nov. is distributed in Belize, Guatemala, El Salvador, Honduras, Nicaragua, and in the Michoacán, Oaxaca, and Chiapas states in Mexico. In these countries, this species has been collected at elevations above from 311 to 2600 m on six pine species, and it commonly occurs in syntopy with D. frontalis.